This invention relates to a transmission fluid cooling system and more particularly to a cooler-bypass unit having a banjo bolt incorporating a relief valve.
Vehicles are typically equipped with transmissions that provide different speed ratios between the engine and the drive axles. A transmission typically generates a good deal of heat, and thus oil is circulated to cool the transmission components.
The oil in the transmission becomes quite hot during operation of the vehicle. Thus, the oil is typically routed to a cooling unit. The cooling unit cools the oil which is then returned to the transmission.
Typically, the transmission is spaced some distance from the cooling unit. As such, fluid lines, such as conduits or hoses must travel the distance from the transmission to the cooling unit. The oil travels between the transmission and cooling unit through the fluid lines.
When the engine is running, oil is continuously being moved to the cooling unit, and from the cooling unit back to the transmission. When the vehicle is cool, the oil is relatively viscous and does not flow quickly through the cooling unit. This causes back pressure on the supply line leading to the cooling unit. For this reason, some transmission cooling units have incorporated a relief valve for returning a portion of the transmission fluid from the supply line leading to the cooling unit directly back into the return line leading back to the transmission. In the past, the relief valve is installed between a T-connector in the supply line and a T-connector in the return line. The separate components result in an unduly high amount of fluid connections, and also additional parts which require additional assembly time.
The more fluid connections that are created in a transmission cooling system, the more places there are that could potentially leak. A transmission oil leak could be very damaging to the vehicle, and could lead to seizure of the transmission. Thus, the relatively high number of fluid connections is undesirable.